JPH1029820A - Nickel-cobalt multiple hydroxide, its production and stock of active material of positive electrode for lithium secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing Ni-CO multiple hydroxide useful as stock of Li-Ni-Co multiple oxide used as the positive electrode material of a lithium secondary battery. SOLUTION: This Ni-Co multiple hydroxide is grains of Ni-Co multiple hydroxide formed from Ni and Co in the state of a solid soln. and/or in a coprecipitated state. The grains constitute practically spherical secondary grains formed by laminating and aggregating primary grains having one or more of platy, columnar and acicular grain shapes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Ni-Co composite hydroxide, a method for producing the same, and a raw material for a positive electrode active material for a lithium secondary battery.

[0002]

2. Description of the Related Art In recent years, portable electronic devices have become more portable.
As cordless technology has rapidly progressed, lithium secondary batteries have begun to be used as power sources for small electronic devices. Regarding this lithium secondary battery, Mizushima et al. Reported in 1980 that lithium cobaltate was useful as a positive electrode active material for lithium secondary batteries [“Material Research Brain” vo1.115, pp. 783-789 (1980). )], Research and development on lithium-based composite oxides have been actively promoted, and many proposals have been made so far.

For example, Li _1-a NiO ₂ (where 0 ≦ a
≦ 1) (US Pat. No. 4,302,518), Li _b Ni
_2-b O ₂ and LiNi _1-d Co _d O ₂ (provided that 0.84 ≦ b
≦ 0.5) (JP-A-2-40861), Li _n Ni _m Co
A composite oxide mainly composed of lithium and a transition metal, such as _1- mO ₂ (JP-A-63-299056, JP-A-1-120765, JP-A-1-42056), has been proposed.

Among the above compounds, lithium cobalt oxide has been studied from the earliest due to its high crystal stability. However, cobalt as a raw material is rare and expensive, and the crystallinity deteriorates when charged to 0.7 electrons or more. And the decomposition of the electrolytic solution is not suitable for increasing the capacity. on the other hand,
LiNiO ₂ has the advantage that it is less expensive than lithium cobalt oxide, but has a poor stability as an active material because it tends to cause defects in the crystal, and also has a discharge capacity when incorporated into a battery. Since the properties are inferior to those of the cobalt type, there are considerable problems in practicality.

[0005]

SUMMARY OF THE INVENTION
A composite lithium metal salt in which nickel is partially substituted with cobalt has been studied from an economic and functional viewpoint. However, as a method of producing cobalt-containing lithium nickel oxide, a method of simply mixing the respective raw materials of oxides and hydroxides of cobalt and nickel and lithium hydroxide in a dry manner and firing the mixture is known. According to the method, defects are easily generated in the crystal, and therefore, those having favorable discharge capacity characteristics have not been obtained.

In view of the above facts, the inventors of the present invention have conducted intensive studies on Ni-Co compounds as raw materials for batteries, and as a result, have found that Ni-Co compounds as raw materials for lithium composite oxides are excellent.
Succeeded in finding a composite hydroxide particle and a method for producing the same, and completed the present invention. Accordingly, an object of the present invention is to provide a novel and novel Ni-Co-based composite hydroxide useful as a raw material of a Li-Ni-Co-based composite oxide effectively used as a cathode material of a lithium secondary battery and the like. It is to provide a manufacturing method thereof.

[0007]

That is, a Ni—Co-based composite hydroxide according to the present invention for solving the above-mentioned problems is:
Ni-Co-based composite hydroxide crystal particles formed in a solid solution and / or coprecipitation state of nickel and cobalt, wherein the crystal particles have a plate-like, columnar or needle-like particle shape,
Alternatively, it is a fundamental feature that a substantially spherical secondary particle is formed by laminating and aggregating primary particles having a particle shape in which these are mixed.

Further, nickel and cobalt have an atomic ratio N
i: Co is in the range of 0:10 to 10: 0, and the particle size distribution of the spherical secondary particles obtained by a measurement method using a laser method is such that (V95−V5) / V50 is 3 or less, and the average particles are The second and third features of the invention are that the diameter is in the range of 1 to 50 μm.

The method for producing a Ni—Co-based composite hydroxide according to the present invention is directed to a method for producing a precipitate of nickel hydroxide and cobalt hydroxide based on alkaline hydrolysis of a mixed salt aqueous solution of a nickel salt and a cobalt salt. In a mixed salt aqueous solution of a salt, in the presence of a chelating agent having a complexing power for metal ions of nickel and cobalt, a precipitation generation reaction by alkali hydrolysis is continuously performed, and then a precipitation product is required. Sufficient aging is a structural feature.

In addition, the above-mentioned continuous precipitation forming reaction is carried out in a multistage manner, and the chelating agent is at least one selected from aminocarboxylic acids, oxycarboxylic acids or ammonia.
The second or third species, respectively,
The feature of. Further, the raw material for a positive electrode active material for a lithium secondary battery according to the present invention is characterized in that the above-mentioned Ni—Co-based composite hydroxide is used as an active ingredient.

The Ni—Co composite hydroxide of the present invention is a Ni—Co composite hydroxide formed in a solid solution and / or coprecipitation state of nickel and cobalt. Here, what is formed in a solid solution and / or coprecipitation state of nickel and cobalt is not, for example, a simple mixture of nickel and cobalt, but an atom at a lattice point of a crystal phase of nickel is one of cobalt and cobalt. Some are partially substituted, and those in which nickel salt and cobalt salt are uniformly coprecipitated. When nickel or cobalt which is not dissolved or coprecipitated is present alone, powder X-ray diffraction indicates that the nickel or cobalt as an impurity formed due to the presence of nickel or cobalt is hydroxylated. An object peak is observed. The Ni—Co-based composite hydroxide of the present invention has very few such impurities, and there is almost no peak in powder X-ray diffraction.

In the particle characteristics of the Ni—Co composite hydroxide according to the present invention, the shape and surface state of the particles can be mostly confirmed by an electron microscope, and the primary particles are plate-like, column-like or needle-like. Unique particle structure in which these primary particles have a laminar particle shape or a particle shape in which they are mixed, and these primary particles are stacked on each other and aggregate to form a substantially spherical secondary particle Is formed. Here, the substantially spherical secondary particles refer to those having a true spherical shape, an elliptical shape such as an egg, or a cocoon-like or dumpling-like shape in which some spherical particles are combined.

Nickel and cobalt have an atomic ratio of Ni: C
Although o is preferably in the range of 0:10 to 10: 0, the size of the plate-like, columnar, or acicular primary particles and the thickness of the laminated layer in the generated crystal particles are the above-mentioned atomic ratios of nickel and cobalt. Depending on the ratio, for example, as the atomic ratio of cobalt increases, the size of plates, columns or needles of primary particles increases, and the thickness of the laminate tends to increase.

The spherical secondary particles have a particle size distribution obtained by a measuring method using a laser method, [(V95−V5) / V50] =
Those having a range of 3 or less are preferred. When the particle size distribution is out of this range, the range of the particle size is widened, which is not preferable as a raw material for a lithium secondary battery. The average particle diameter of the spherical secondary particles is preferably in the range of 1 to 50 μm,
The range of ２０20 μm is more preferable.

The Ni—Co composite hydroxide according to the present invention has the above-mentioned particle characteristics. When used as a positive electrode active material for secondary batteries, it has unprecedented superior discharge characteristics and discharge retention,
It is particularly useful as a raw material for this active material.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The production method according to the present invention will now be described. In an alkaline hydrolysis reaction of a mixture of a nickel salt and a cobalt salt, a nickel and cobalt metal solution is mixed with an aqueous solution of a mixed salt of the nickel salt and the cobalt salt. In the presence of a chelating agent having a complexing power for ions, a precipitation-forming reaction is continuously performed by alkali hydrolysis, and then the precipitation product is aged for a necessary and sufficient residence time. is there.

The nickel salt used in the present invention is not particularly limited as long as it is soluble in water, and usually includes easily water-soluble mineral salts such as nickel sulfate, nickel nitrate and nickel chloride. The cobalt salt is not particularly limited as long as it dissolves in water similarly to nickel, and usually includes easily water-soluble mineral salts such as cobalt sulfate, cobalt nitrate, and cobalt chloride. The nickel salt and the cobalt salt are preferably used in the reaction at an aqueous solution concentration of about 0.5 to 3.5 mol / L within a practical range.

As the chelating agent having a complexing power for these metal ions, for example, at least one or more selected from aminocarboxylic acids, oxycarboxylic acids and ammonia are preferable. As aminocarboxylic acids, for example, hydrazine, triethanolamine,
Examples include glycine, alanine, asparagine, iminodiacetic acid, glutamic acid, ethylenediamine, ethylenediaminetetraacetic acid, and salts thereof. Examples of the oxycarboxylic acid include acetic acid, lactic acid, oxalic acid, malonic acid, malic acid, tartaric acid, citric acid, salicylic acid, thioglycolic acid, and salts thereof.

The ammonia is not particularly limited as long as it can supply ammonium ions. Examples of the ammonia include aqueous solutions of ammonium salts such as ammonium nitrate, ammonium sulfate, and ammonium chloride, aqueous ammonia, and ammonia gas. Water.

The above-mentioned chelating agent is preferably supplied in the range of 0.2 to 4.0 mol per mol of the nickel salt and the cobalt salt. The chelating agent may be supplied alone, or may be added to any of the nickel salt aqueous solution and the cobalt salt aqueous solution by mixing at a predetermined ratio. If the amount is less than 0.2 mol, the grain growth is not sufficient, and if it exceeds 4.0 mol, no more remarkable effect can be expected and an economic problem occurs, which is not preferable.

The alkali used for the alkali hydrolysis is
A caustic aqueous solution such as sodium hydroxide or potassium hydroxide is preferred, but sodium hydroxide is most preferred.
The addition amount of the alkali is preferably from 1.1 to 3.0 mol per 1 mol of the nickel salt and the cobalt salt, and when less than 1.1 mol, unreacted nickel salt and the cobalt salt are easily generated. When more than 3.0 moles are added,
Particle growth is not sufficient and many ungrown particles are likely to be generated.

When a precipitation reaction of a metal hydroxide is carried out by using the above-mentioned raw materials, several modes can be considered as a reaction operation. The embodiment is illustrated below. (1) In the production reaction of a metal hydroxide based on alkali hydrolysis, the aqueous solution of the metal salt, the chelating agent and the alkali agent are continuously quantitatively maintained while keeping the pH in the reaction system constant in the range of 9 to 12 throughout. It is a method of adding to. By this operation, hydroxides of nickel and cobalt accompanying the hydrolysis of the metal salt are continuously produced as homogeneous coprecipitates under stable conditions throughout. Next, it is necessary to subject the produced coprecipitate to a necessary and sufficient aging treatment in the same reactor or another receiver. (2) As a second method, there is a case where an alkali agent is added to an aqueous metal salt solution containing a chelating agent to form a coprecipitate by alkali hydrolysis, and then ripening is performed in the same manner. (3) As another method, the amount of the reaction solution in the system is controlled to be constant except for the reaction medium solution without overflowing the reaction system slurry containing the coprecipitated product by continuously adding the reaction solution. This is a method of reacting and aging while reacting.

In any case, this aging is carried out after precipitation
Desirably, stirring is performed for at least 3 hours. Further, it is desirable to set the reaction conditions so that the slurry concentration of the reaction system is at least 70 g / L or more. If the concentration is lower than this, the particle growth becomes extremely slow or the processing capacity increases, which is not preferable. This reaction operation may be a batch method, but is preferably a continuous method, or may be a multi-stage method in which the reaction is performed several times in the continuous method. The reaction temperature is usually 10
To 100 ° C, more preferably 20 to 80 ° C
It is. The reaction time is about 1 to 72 hours.

The Ni-Co obtained by the above-mentioned manufacturing method
The composite hydroxide has a substantially spherical particle form, is useful as a raw material for a positive electrode active material of a lithium secondary battery, and has the Ni-Co composite hydroxide as an active ingredient. A lithium secondary battery using a positive electrode active material has excellent characteristics such as discharge capacity and discharge retention.

[0025]

【Example】

Example 1 200 mL of water was placed in a 1-L beaker in advance,
NiSO of 1.6mol / L ₄ · 6H ₂ O and 0.4mo
_{l / L CoSO 4 · 7H 2} O aqueous solution of mixed salts of 1200
mL, 6 mol / L NaOH solution 800 mL, and 1.5 mol / L ammonia solution 400 m as a complexing agent
L while dropping L and adjusting the pH to 11.
The mixture was kept warm at ℃ to form a hydroxide, and then aged for 9 hours with stirring. During this time, the amount of liquid in the system is controlled by the over method,
The liquid that overflowed was replaced every hour.

The hydroxide formed after the filtration was subjected to repulping washing. After sufficient cleaning while judging the cleaning effect with a conductivity meter, and drying, X-ray diffraction of the precipitated product showed that the precipitated product was not amorphous, and Ni and Co were dissolved in each other. Eutectic of Ni and Co, with a composition of Ni /
It was confirmed that Co was approximately 8/2. FIG. 1 shows an SEM photograph of the precipitated crystals. From FIG. 1, it can be seen that this crystal has a primary particle having a columnar particle shape, and these primary particles are aggregated to form a particle form constituting a substantially spherical secondary particle.

Example 2 200 mL of water was poured into a 1 L beaker in advance,
NiSO of 1.8mol / L ₄ · 6H ₂ O and 0.2mo
_{l / L CoSO 4 · 7H 2} O aqueous solution of mixed salts of 1200
mL, 800 mL of a 6 mol / L NaOH solution, and 400 mL of a 1 mol / L glycine solution as a complexing agent were added dropwise, and the pH was adjusted to 10 while keeping the temperature at 70 ° C. to precipitate hydroxides. The mixture was stirred and aged for 9 hours. During this time, the amount of liquid in the system is controlled by the overflow method,
The overflowed liquid was replaced every three hours.

The precipitated product obtained after the filtration was repulped and washed. After sufficiently washing while confirming the washing effect with a conductivity meter, and drying, X-ray diffraction was performed on the precipitate product. As a result, the precipitate product was crystal particles composed of a eutectic of Ni and Co, and the composition was It was confirmed that Ni / Co was about 9/1. In addition, like the crystal particles obtained in Example 1, the crystal particles had a particle form in which columnar primary particles were aggregated to form substantially spherical secondary particles.

[0029] Example 3 capacity 500mL beaker, tension of water in advance 250 mL, and NiSO ₄ · 6H ₂ O in 1.4 mol / L 0.6
mol / L CoSO of ₄ · 7H ₂ O aqueous solution of mixed salts of 2
L, 1300 ml of a 6 mol / L NaOH solution, and 670 mL of a 1 mol / L malic acid solution as a complexing agent were added dropwise, and the mixture was kept at 70 ° C. while adjusting the pH to 10 to precipitate hydroxides. The mixture was stirred and aged for 15 hours.
During this time, in order to control the amount of liquid in the system, the slurry concentration was increased while only the reaction medium liquid was removed by filtration under reduced pressure.

After filtration, the precipitated product was repulped and washed.
Thoroughly clean the conductivity meter while judging the cleaning effect,
X-ray diffraction was performed on the precipitated product after drying. As a result, the precipitated product was a crystal composed of a eutectic of Ni and Co.
It was confirmed that i / Co had a composition of about 8/2. Further, the crystal particles, like the crystal particles obtained in Example 1, are laminated with primary particles having a plate-like particle shape,
It had a particle form that aggregated to form substantially spherical secondary particles.

[0031]

According to the present invention, there is provided a Ni-Co-based composite hydroxide useful as a raw material of a Li-Ni-Co-based composite oxide particularly used as a cathode material of a lithium secondary battery, and a method for producing the same. Is done. When the Ni-Co-based composite hydroxide is used as an active component of a positive electrode active material, a lithium battery having extremely excellent discharge capacity characteristics can be obtained.

[Brief description of the drawings]

FIG. 1 is an SEM photograph showing a particle structure of a crystal particle of a Ni—Co-based composite hydroxide of the present invention.

FIG. 2 is an SEM photograph when the particle structure of the crystal particle of FIG. 1 is observed at a higher magnification.

Claims (7)

[Claims] 1. A crystal particle of a Ni—Co-based composite hydroxide formed in a solid solution and / or coprecipitation state of nickel and cobalt, wherein the crystal particle has a plate-like, columnar or needle-like particle shape. Or a substantially spherical secondary particle formed by laminating and aggregating primary particles having a mixed particle shape. 2. Nickel and cobalt have an atomic ratio of N
The Ni-Co composite hydroxide according to claim 1, wherein i: Co is in a range of 0:10 to 10: 0. 3. The particle size distribution of the spherical secondary particles determined by a measuring method using a laser method is such that (V95−V5) / V50 is 3 or less, and the average particle diameter is in the range of 1 to 50 μm. The Ni-Co-based composite hydroxide according to claim 1 or 2, wherein: 4. A method for producing a precipitate of nickel hydroxide and cobalt hydroxide based on alkaline hydrolysis of an aqueous solution of a mixed salt of a nickel salt and a cobalt salt, wherein a metal ion of nickel or cobalt is added to the aqueous solution of a mixed salt of a nickel salt and a cobalt salt. Ni-Co-based composite water characterized in that a precipitation-forming reaction by alkali hydrolysis is continuously performed in the presence of a chelating agent having a complexing power with respect to A method for producing an oxide. 5. The method for producing a Ni—Co-based composite hydroxide according to claim 3, wherein the continuous precipitation generation reaction is performed in a multistage manner. 6. The chelating agent is at least one selected from aminocarboxylic acids, oxycarboxylic acids and ammonia.
The Ni-Co according to claim 4 or 5, wherein the Ni-Co is a kind or two or more kinds.
For producing a composite hydroxide. 7. The Ni according to claim 1, 2 or 3
-A positive electrode active material raw material for a lithium secondary battery containing a Co-based composite hydroxide as an active ingredient.